Heavy oil containing carbonate and sand reservoirs exhibits reverse wettability characteristics. Depending on temperature, the phase of injected steam, and rock type, the wettability may be altered to more water-wet. The addition of chemicals to hot-water (or steam) may further change the interfacial properties (more water-wet and less interfacial tension). Surfactants were tested extensively for this process in the past and their temperature resistance was an obstacle. New generation chemicals need further investigation from a technically and economically success point of view.
The objective was to investigate the alteration of interfacial properties induced by different types of chemical agents under hot conditions. To achieve this, three experimental tools (contact angle measurement, interfacial tension measurement, and spontaneous imbibition tests) were applied. High pressure and high temperature contact angle measurements enabled a quick method to identify the suitability of the chemicals for wettability modification. Interfacial tension between oil and different chemical solution was measured with a variation of temperature. In the imbibition tests, core samples were exposed to heating for longer time periods so that the temperature resistance of the chemicals was also tested. Imbibition experiments were conducted at ambient pressure and 90°C. The combination of the contact angle and interfacial tension provided insight into the recovery enhancement mechanisms.
Six different chemicals including an ionic liquid, three nano-fluids (silica, aluminum, and zirconium oxides), a cationic surfactant, and a high pH solution were chosen based on our screening study. Heavy-oil used was obtained from a field in Alberta (6,000cp). Contact angles were measured on mica, calcite, sandstones and limestones plates. The experimental temperature ranged from 25 to 200°C and pressure was changed to keep the solution in the aqueous phase. Promising modifiers for different rock types under different temperature were screened separately. Secondly, spontaneous imbibition tests were performed on sandstone and limestone cores with screened promising modifiers. Oil recovery in this phase was continuously monitored to evaluate wettability alteration capability and the mechanism(s) involved was analyzed for different chemicals.
Analysis of wettability alteration mechanisms and IFT reduction capabilities is expected to be useful in the selection of suitable and temperature-resistant chemicals for high temperature applications in different reservoir rocks.